Voice compressor circuit

The amplifier drives the base of a PNP-type MPS6517 transmitter with a voltage gain of approximately 20. The controller RI changes the quiescent Q-point of the transistor, that is, the amount of signal that exceeds the level Vr. Only when the peak value is greater than Vr (Vr≈7.0V), diode D1 can rectify the positive output peak of Q1. The resulting output filters Cx and Rx. Rx controls the charging time constant or dispatch time. Cx is required for both charging and discharging.